(a) Field of the Invention
The invention relates to a backlight module having improved light utilization efficiency and a light guide plate used in the backlight module.
(b) Description of the Related Art
Nowadays, various well-known methods have been used to form a light guide plate with microstructures (light scattering pattern). For example, an isotropic etching process is performed on a steel plate to produce a stamper having a micro-dot pattern. However, defects on an etched steel substrate often occur to lower the repeatability of the light scattering pattern on different light guide plates. Further, an isotropic etching process proceeding with equal velocities in all directions is hardly to avoid the formation of enlarged etch holes and fails to control the inclination surface angle of each microstructure to result in an unsatisfied luminous efficiency of a light guide plate.
Hence, another design where a machining tool is used to produce V-shaped notches is proposed to effectively control the inclination surface angle of each microstructure. Though such method may achieve a better luminous efficiency, its fabrication process is complicated because of the great demand for an accurate control on the dimension, positioning, and machining amount of a work piece. Besides, since the electronic product is made to be thinner and thinner on current trends, the V-shaped notches formed on a thin light guide plate are inevitably to have a shallow depth to result in the complexity of their fabrication processes.
Thus, another design where an anisotropic etching process is performed on a crystalline material is proposed to avoid the above problem. Since the anisotropic etching proceeds with different velocities in different directions in a single crystal to create a specific shape, it may achieve a high repeatability of the light scattering pattern on different light guide plates.
However, in all the above conventional designs, the inclination surface angles of the microstructures are not optimized to thus fail to further improve the luminous efficiency as well as the light utilization efficiency.